Magneto-optical recording media have been in practical use as rewritable magneto-optical recording media. Information is recorded on and reproduced from the magneto-optical recording medium with the use of a light beam which is emitted by a semiconductor laser and converged on the magneto-optical recording medium. A problem with such conventional magneto-optical recording media is that their reproduction characteristics deteriorate when recording bits serving as magnetic recording domains have too small diameter and intervals, in comparison with the diameter of the light beam.
The cause of such a problem is that the light beam converged on a target recording bit covers within its diameter not only the target recording bit, but also a neighboring recording bit, and that each recording bit therefore cannot be reproduced independently.
Japanese Laid-Open Patent Application No. 150418/1994 (Tokukaihei 6-150418) discloses a magneto-optical recording medium capable of solving the above-mentioned problem. The magneto-optical recording medium is constructed to have a non-magnetic intermediate layer between a recording layer and a readout layer. The readout layer is in an in-plane magnetization state at room temperature, and changes into a perpendicular magnetization state with a rise in temperature. In this structure, magnetostatic coupling is achieved between the recording layer and readout layer through the non-magnetic intermediate layer therebetween. In a portion of the readout layer which is in the perpendicular magnetization state, the magnetization of the recording layer is copied. On the other hand, a portion of the readout layer, which exhibits the in-plane magnetization state, masks the magnetization of the recording layer. This structure does not allow reproduction of information of a recording bit in a portion of the recording layer, which is adjacent to the portion of the readout layer exhibiting the in-plane magnetization state. It is therefore possible to reproduce each recording bit independently even if the converged light beam covers the target recording bit to be reproduced and a neighboring recording bit within its diameter.
However, it has been confirmed that the magneto-optical recording medium disclosed in the above-mentioned document has a problem in reproducing information which is recorded with a smaller recording bit diameter at smaller recording bit intervals. Namely, sufficient masking cannot be achieved by the in-plane magnetization, and sufficient reproduced signals are not obtained.